ㄹ까 보다

afraid that; just in case

Names something bad the speaker is worried might happen. Every line here pairs it either with a fear word — 걱정이에요, 불안해요, 조마조마, 조심스러운 — or with an action taken to head the outcome off: 네 언니 알까 봐 내 명의로 받은 건데 'I put it in my name in case your sister found out.' The feared event is something outside the speaker's control, never their own plan. Keep it apart from ㄹ까 하다, the near-identical shape that means 'I'm thinking of doing it' and has no fear in it.

Register: conversational; these lines are all casual or plainly polite